The present invention relates to land vehicles and, more particularly, to utility vehicles adapted for multi-terrain use.
A variety of multiple-wheeled utility vehicles have been designed for light-duty work over a variety of terrain conditions. Many such vehicles include small beds or boxes for carrying modest loads. Typically, these vehicles have one or two steerable front wheels and at least two rear drive wheels. To increase the hauling capacity and the size of the load-carrying zone, some of these vehicles have been equipped with four or more rear drive wheels positioned under the hauling bed. Chain drives are commonly used in vehicles of this power class for transferring power from one set of drive wheels to another. In general, such chain drives are efficient, relatively inexpensive and easy to maintain and repair, as compared with more complicated drive systems that use intermeshed drive shafts and differentials.
However, in prior art utility vehicles utilizing a chain drive for four or more rear drive wheels, the rear drive wheels are unsuspended or are inadequately suspended. In some prior art utility vehicles utilizing a chain drive for four or more rear drive wheels, the rear drive wheels are not suspended at all, and remain in fixed positions relative to the vehicle frame. While unsuspended drive wheels work well with chain drives (which require the sprockets carrying the chain to remain in substantially the same plane to ensure proper operation and avoid disengagement of the chain), they compromise the vehicle""s performance and limit the types of terrain on which the vehicle can be effectively used.
Thus, there is a need for a multi-terrain utility vehicle having multiple rear drive wheels all powered by a simple chain drive system, wherein each of the rear drive wheels is independently suspended from the vehicle frame for optimal performance and terrain versatility.
A general object of the invention is to provide a utility vehicle having multiple drive wheels for traversing a variety of terrain conditions. Another object is to provide a vehicle drive system that is efficient, relatively inexpensive and easy to maintain and repair. A related object is to provide chain-drive and suspension systems for utility vehicles that have fewer and less expensive parts than more complicated drive and suspension systems used in vehicles of the same power class, without significantly compromising performance. Still another object of the invention is to provide an idler mechanism for a chain drive that permits significant transverse movement of the drive chain without compromising performance of the drive system. A more specific object of the invention is to provide a drive system for a multi-terrain utility vehicle having multiple, chain-driven rear drive wheels that are each independently suspended from the vehicle frame.
In general, a vehicle drive system of the present invention comprises a frame, a motor, a first wheel assembly, a second wheel assembly and a drive chain. The motor is mounted to the frame and has a motor shaft powered by the motor. The first wheel assembly comprises a first control arm, a first axle, a first sprocket and a first wheel. The first control arm extends generally transversely from the frame and has a proximal end pivotally connected to the frame in a manner to permit pivoting movement of the first control arm in a generally vertical arcuate path relative to the frame. The first axle is journalled in the first control arm for rotation relative thereto. A proximal end of the first axle is operatively connected to the motor shaft in a manner so that rotation of the motor shaft causes rotation of the first axle. The first sprocket and first wheel are both fixedly mounted to the first axle. Similarly, the second wheel assembly comprises a second control arm, a second axle, a second sprocket and a second wheel. The second control arm extends generally transversely from the frame and generally parallel to the first control arm. The second control arm has a proximal end pivotally connected to the frame in a manner to permit pivoting movement of the second control arm in a generally vertical arcuate path relative to the frame. The second axle is journalled in the second control arm for rotation relative thereto. The second sprocket and second wheel are both fixedly mounted to the second axle. The drive chain is trained around the first and second sprockets in a manner so that rotational motion of the first sprocket causes rotational motion of the second sprocket.
In another aspect of the invention, a vehicle drive system comprises a frame, a motor, a first wheel assembly, a second wheel assembly and an endless drive member. The motor is mounted to the frame and has a motor shaft powered by the motor. The first wheel assembly includes a first axle, a first drive wheel and a first riding wheel. The first axle extends generally transversely from the frame and is journalled for rotation relative to the frame. A proximal end of the first axle is operatively connected to the motor shaft in a manner so that rotation of the motor shaft causes rotation of the first axle. The first axle is operatively connected to the frame in a manner so that a distal end of the first axle is moveable in a generally vertical arcuate path relative to the frame about a first pivot axis. The first drive wheel and the first riding wheel are both mounted to the first axle. Similarly, the second wheel assembly includes a second axle, a second drive wheel and a second riding wheel. The second axle extends generally transversely from the frame and generally parallel to the first axle. The second axle is journalled for rotation relative to the frame and is operatively connected to the frame in a manner so the distal end of the second axle is moveable in a generally vertical arcuate path relative to the frame about a second pivot axis. The second drive wheel and the second riding wheel are both mounted to the second axle. The endless drive member is trained around the first and second drive wheels in a manner so that rotational motion of the first drive wheel causes rotational motion of the second drive wheel.
In still another aspect of the invention, a vehicle drive system comprises a frame, a motor, a drive sprocket, a wheel assembly and a drive chain. The motor is mounted to the frame and has a motor shaft powered by the motor. The drive sprocket is operatively connected to the motor shaft in a manner so that rotational motion of the motor shaft causes rotational motion of the drive sprocket. The wheel assembly includes an axle, a follower sprocket and a wheel. The axle is journalled for rotation relative to the frame and is operatively connected to the frame in a manner so a distal end of the axle is moveable in a first generally vertical arcuate path relative to the frame about a pivot axis. The follower sprocket is fixedly mounted to the axle in a manner so that the follower sprocket is moveable in a second generally vertical arcuate path relative to the frame about the pivot axis. The wheel is mounted to the distal end of the axle. The drive chain is trained around the drive sprocket and the follower sprocket in a manner so that rotational motion of the drive sprocket causes rotational motion of the follower sprocket.
While the principal advantages and features of the present invention have been described above, a more complete and thorough understanding and appreciate for the invention may be attained by referring to the drawings and description of the preferred embodiments, which follow.